The CD control of the first lithography (L1) patterns is a important issue in the single-etch double patterning (SEDP)
process. In this process, L1 patterns are cured either chemically or thermally and then subjected to the second
lithography (L2). A chemical curing process using a surface curing agent (SCA) often results in the CD growth due to
the "positive" interaction between the first and second resists. A thermal curing process using a thermal cure resist
(TCR) often results in the CD loss due to the volumetric shrinkage of the L1 patterns during the L2 process. By
combining SCA and TCR concepts, we developed a simple "hybrid" curing system which offers precise control of the
L1 CD after double patterning. This hybrid curing system involves thermal curing followed by a liquid rinse process
using a double patterning primer (DPP). DPP is an aqueous solution formulated with SCA components and enhances
"positive" interaction between L1 and L2 patterns. While CD loss of 5~6nm is observed without DPP treatment, ~11nm
CD growth was observed with TCR after DPP treatment. The L1 CD after double patterning was precisely controllable
by post-priming bake process with the rate of -0.3nm/°C in the temperature ranging from 120 ~ 150°C. Taking
advantage of the CD growth with DPP treatment, we further developed three different advanced patterning schemes: 1.
"Shrink Process Assisted by Double Exposure" (SPADE I), 2. "Space Patterning Assisted by Double Exposure"
(SPADE II), and 3. "Sidewall Patterning Assisted by Double Exposure" (SPADE III). Using SPADE I, contact hole CD
was reduced by 10~30nm and excellent through pitch performance was observed. SPADE I can also improve
LER/LWR when used in the formation of smaller trenches. SPADE II was developed for self-aligned pitch splitting of
contact holes and SPADE III was developed for self-aligned pitch splitting of lines. In this paper, the use of DPP in
various SPADE technologies is described and its potential in the advanced patterning schemes is discussed.
Two different pattern curing techniques were developed to stabilize first lithographic images for the single-etch double
patterning process. The first method uses a surface curing agent (SCA) that is coated on top of the patterned surface to
form a protective coating layer during the curing bake process. It was found that the surface curing process with SCA
offers minimum CD changes before and after the double patterning process. Virtually no CD change was observed with
the first lithographic images at various curing bake temperatures ranging from 120 ~160°C indicating the curing reaction
is limited on the patterned surface. The second method uses a thermal cure resist (TCR) that is a special 193nm
photoresist with a crosslinkable functional group to form an insoluble network upon heating at higher temperature. A
single-step curing process of the first lithographic images was achieved using TCR by baking the patterned images at
180°C for 60sec. A cross-line contact hole double patterning method was used to evaluate these two different curing
techniques and both SCA and TCR successfully demonstrated their capability to print 45nm contact holes with excellent
CD uniformity in immersion lithography (1.35NA) with a 45nm half pitch mask. It was also confirmed that both SCA
and TCR can be extended to the top-coat free immersion double patterning process using an embedded barrier layer
A new methodology that allows monitoring the deprotection kinetic of UV sensitive thin resist films was recently
developed at LTM. This tool measures by ellipsometry changes in optical properties of thin resist films heated at a PEB
temperature and exposed to UV.
This article presents results of the deprotection kinetic of model resist supplied by Rohm and Haas. Films thicknesses
range from 58nm to 150nm. Two thermal protocols were used to check an impact of the film thickness on the
deprotection kinetic. The first one is a thermal ramp were temperature increases at a given rate. Prior to this ramp the
sample was exposed to UV for 60s with the help of a broadband Xe lamp. This protocol allows detecting the temperature
that initiates the deprotection reaction into the film. The second test consists in heating the samples at a fixed temperature
for a given time and to expose to UV the film at this temperature. This studies supplies information on the deprotection
kinetic occurring in the film at this temperature.
The work we did on 193 nm resist films clearly shows that this technique can monitor both the thermal initiation of the
deprotection and the real time measurement of the compaction kinetic of the film during the PEB. The initial film
thickness impact on the deprotection kinetic is presented in this paper to check whether lithography processes should be
adapted to the film thickness.
Resolution and accuracy needs for the most advanced nodes, as well as fab capacities management are requirements that
encourage the use of ArF resists for post-gate implant levels.
In this paper, we investigate several key integration criteria that an ArF resist needs to fulfill to be used for implant
applications. Outgassing level is followed during the first seconds of the implantation step and is systematically found
under the chamber pressure limit. As well, stopping power efficiency is evaluated. SIMS analysis and simulation tests
with SRIM software are performed to define the minimum resist thickness that prevents ions to penetrate the layers
underneath. Data indicate that both experimental and simulation tests are in good agreement and that at low energies the
stopping layer thickness is found to be in the order or lower than 80 nm. Finally, the impact of implantation step on
patterned wafers is carried out. Features of interest are dense and isolated lines with a nominal CD of 130 nm. We
control the CD and profile with a standard CD SEM and a CD AFM in order to get access to additional information such
as height of the feature, top rounding and the CD through height. Results underline that our patterned resist doesn't show
significant degradation under our implant conditions.
Proc. SPIE. 6518, Metrology, Inspection, and Process Control for Microlithography XXI
KEYWORDS: Lithography, Etching, Diffusion, 3D modeling, Atomic force microscopy, Scanning electron microscopy, Photoresist materials, Line width roughness, Critical dimension metrology, Line edge roughness
The improvement of devices performances is due to many factors such as new architectures, new materials
and better lithography resolution. Resist chemical components play a key role in the final performance of a
specific resist. In addition to resist characteristics such as: resolution, etching selectivity, the final resist line
edge roughness (LER) and line width roughness (LWR) becomes a critical issue because it can degrade
resolution and linewidth accuracy and causes fluctuations of transistors performances<sup>1,2</sup>. LER and LWR are
currently calculated with top-down view SEM images. With chemically amplified resists, we can play on
photoacid generator size to partially control acid diffusion length during the post exposure bake.
In this paper we propose to compare two techniques, the CD-AFM and CD SEM in order to study the
impact of various acid diffusion lengths on LER and LWR. The results show that globally the two
techniques agree on most of the results and show the same trends. However, when the profiles vary the
linearity between the two techniques can vary drastically. In addition, as a complementary technique to the
CD-SEM technique, the CD-AFM gives additional information such as height (top loss), top rounding and
sidewall angle which allow us to understand more deeply the impact of PAG size. Therefore, these
additional information have a non negligible impact on near term new resist development and lithography
processes development. As an illustration of this work, we will present the latest resist development coming
from this understanding and leading to very low LER and LWR. Finally, we will propose strengths and
weakness of each technique.
In this study we investigate the pattern collapse mechanism of dense patterns with resolution under 60nm printed in Extreme Ultra Violet (EUV-IL) and Electron Beam Lithographies (EBL). Pattern collapse occurs when physical properties of the material can't imbalanced the capillary force exerted on the pattern during the drying of the rinse liquid. In former simulation models, the height of the pattern at which collapse occurs (critical height, H<sub>c</sub>) was predicted using either elastic deformation properties, or plasticizing limit value of the resist. Experimental observations of unstuck patterns, lead us to develop 2 new models considering the adhesion properties of the resist film on the substrate. By comparing simulated to experimental results for varying pattern pitchs printed in 2 Chemically Amplified Resists (CARS), we show that pattern collapse behaviour of EUV-IL and EBL patterns is not only ruled by rigidity or strength of the resist but can be perfectly described with equation defining the unsticking of a non bending pattern. Finally by using surfactinated solution on sub-60nm dense patterns, great improvements in H<sub>c</sub> values and increase of process window latitude are shown. However, due to larger capillary force, this efficiency decreases with pattern pitch and appears limited on patterns width smaller than 40 nm.